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 A160637 Hankel transform of A114464(n+1). 3
 1, 1, -2, -8, -32, -128, 1024, 16384, 262144, 4194304, -134217728, -8589934592, -549755813888, -35184372088832, 4503599627370496, 1152921504606846976, 295147905179352825856, 75557863725914323419136 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Hankel transform of A114464(n) is A160636. This is a generalized Somos-4 sequence. - Michael Somos, Mar 14 2020 LINKS G. C. Greubel, Table of n, a(n) for n = 0..114 FORMULA a(n) = (-2)^floor(C(n+1,2)/2). 0 = a(n)*a(n+4) - 2*a(n+1)*a(n+3) + 4*a(n+2)^2 = a(n)*a(n+5) - 4*a(n+1)*a(n+4) for all n in Z. - Michael Somos, Mar 14 2020 MATHEMATICA Table[(-2)^Floor[Binomial[n + 1, 2]/2], {n, 0, 50}] (* G. C. Greubel, May 03 2018 *) a[ n_] := (-2)^Quotient[n (n + 1), 4]; (* Michael Somos, Mar 14 2020 *) PROG (PARI) for(n=0, 50, print1((-2)^floor(binomial(n+1, 2)/2), ", ")) \\ G. C. Greubel, May 03 2018 (MAGMA) [(-2)^Floor(Binomial(n+1, 2)/2): n in [0..50]]; // G. C. Greubel, May 03 2018 CROSSREFS Sequence in context: A004171 A009117 A331407 * A183895 A228921 A150829 Adjacent sequences:  A160634 A160635 A160636 * A160638 A160639 A160640 KEYWORD easy,sign AUTHOR Paul Barry, May 21 2009 STATUS approved

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Last modified October 27 01:02 EDT 2020. Contains 338035 sequences. (Running on oeis4.)